The study sought opinions from 6,486 U.S. adult consumers about which companies they thought were most trustworthy and did the best job protecting personal information.

Google ranked 10 in the Ponemon/Trust-e surveys conducted in 2007 and 2006. The company didn't comment on why public perception may have changed, but said that user trust remains critical to its business.

"In our quickly evolving business environment, ensuring that we earn and keep our users' trust is an essential constant for building the best possible products," a Google spokesperson said in an e-mailed statement. "We work hard to earn and keep that trust with a long-standing commitment to protect to the privacy of our users' information. The bedrock of our privacy philosophy is to be transparent about our approach to privacy and to give users meaningful control, and we continue to work to put these principles into practice and improve user privacy."

However, such ratings should be viewed with some skepticism. As last year's survey explained, "... the consumer ratings may not reflect at all the actual privacy practices of the company and its good effort to protect the personal information of its customers and employees. Further, what a company does in the area of privacy and data protection can be invisible to the customer until he or she experiences a data breach and seeks redress or has a question that needs to be answered."

Indeed, the presence in the top 20 this year of Facebook, despite the outcry it faced over the privacy implications of its Beacon advertising system late last year and earlier this year, suggests popularity may weigh more heavily in the rankings than actual practices.